Following initial smoothness tests on the oval and road course at Indianapolis Motor Speedway in August and September, IndyCar’s new IR-28 chassis officially faced its first true durability test on the grueling bumps of Sebring International Raceway.
On Monday, five-time and reigning IndyCar Series champion Alex Palou took the wheel for Honda-powered Chip Ganassi Racing, completing 43 laps around Sebring’s outer loop. The testing duties at the historic Florida venue transition on Tuesday to 2016 Indianapolis 500 winner Alexander Rossi, driving for Chevrolet-powered ECR.
Sebring’s harsh mix of concrete and asphalt makes it an ideal testing venue. By mimicking the rough, unforgiving conditions of temporary street circuits — which accounted for a third of the 2026 race calendar — the track puts component strength and durability under extreme stress before mass production begins.
“We’re trying to test it as tough as we can,” Palou said. “It’s a bumpy course. Before we produce all the new cars, we want to make sure it passes this stress test and that it’s good to go for racing.
“We’re trying to get miles and miles, see what breaks so we can fix it.”
Palou and Rossi remain the exclusive pair of series drivers tasked with testing the IR-28 ahead of its official competition debut at the start of the 2028 season. Alongside Dallara and IndyCar officials, the drivers are working through an extensive checklist covering basic vehicle performance and mechanical systems.
A major focus of Monday’s test was driver comfort and cooling. While the current chassis had cooling ducts retrofitted into its carbon fiber body following the introduction of the aeroscreen in 2020, the IR-28 was designed from the ground up with strategically placed, integrated air ducts. Palou noted that feedback provided during the earlier IMS tests yielded immediate improvements on track at Sebring.
“Yeah, it’s been so much better, the cooling, since we started a couple months ago,” Palou said. “Huge step, and that’s something we’ve been asking for a long time on our current car.
“We have a very big one (duct) right in front of us (on the IR-28) that makes the air go from down to up and makes the airflow so much better. It’s been huge.”
The session also produced a historic milestone: the IR-28’s first on-track overtake. During testing, Palou came up on and passed Kyle Kirkwood (Andretti Global), who was running a Firestone Firehawk tire test alongside Scott McLaughlin (Team Penske).
“It wasn’t planned,” Palou said. “We went out, and I saw Kirkwood was doing the tire test. We spoke during lunch that at some point this afternoon we would go together. We wanted to see how this car does in traffic. It was cool. We were playing a little bit.”
Because Sebring is a mainstay for IndyCar testing, engineers have vast amounts of data from the existing chassis to benchmark against the IR-28. Early indications show all systems operating smoothly as development continues.
“I’m very excited,” Palou said. “I like the looks of it. It seems safer. It looks like it’s going to be much better racing because we’re going to be able to follow much closer on road, street and ovals.
“I’m just excited to go racing. I wish it was already ’27. Having said that, it gives us so much time to work on the car, to make sure it’s good. If there’s something that doesn’t really work on ovals or whatever, we can go test it before we actually race it.”
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